1. Field of the Invention
In the food processing industry it is a well known problem that it is difficult to obtain portions consisting of a number of parts (such as pieces of fresh or frozen fish, meat or poultry) when it is additionally required that a predetermined precise portion weight (possibly with tight tolerances) be combined with a pre-determined number of pieces, in particular in those cases where the weight of the individual pieces deviates in such a manner that the weight distribution of the pieces is non-normal or changing. Portions having a fixed number of pieces or a number in a chosen interval may be aimed at.
A weight distribution may be normal, whereby the usual concepts xe2x80x98average and spreadxe2x80x99 may be used as well as well tested statistical calculation procedures. The weight distribution may also be non-normal, because of the fact that the charge or flow of material being weighed may, at an earlier stage, already have been subjected to sorting and possible removal of all items within certain weight intervals, and this will have removed the possibility for traditional statistical calculations.
2. Description of Related Art
Known methods to obtain portions of the kind discussed comprise manual weighing which is a very stressful activity and in most cases the built-in security for the customer in the form of over-weight means a considerable loss for the manufacturer.
Two principally different automatic methods are known: The combination weighing principle and the accumulation weighing principle. In the first, a number of weighed parts or part portions are disposed in a number of weighing bins or in the combination bins of such weighing bins, whereupon, based on the part weights measured, a computer calculates which bin sub portions in combination will constitute the portion which is closest in weight to the predetermined target weight. The limitation of this method is in particular that the number of parts which is available for the combination is limited. In particular when the individual weights of the parts deviate, possibly considerably from each other (as in the case of fish, poultry, or meat) the combinations will often deviate more than is desirable from the target weight, and this will, as in the manual case, mean a loss for the manufacturer.
In the accumulation weighing principle several full portions are currently and even concurrently built up. The individual parts are conveyed forward in a line and are weighed on a dynamic weigher, and the weights are registered successively by a computer which hence keeps track of the relative position in the line and the respective weights. A distribution unit places the parts selectively in collecting bins, whereby the portions are built up, while the accumulated weights of parts in the individual bins are registered in the computer. The allocation of the individual parts to the various bins continues as long as the accumulated weight in the bin is still below the target weight, until, finally, the bin waits for a part which in the particular portion would just bring the portion weight to the desired value. In order to achieve a reasonable capacity one will have to accept that it may become necessaryxe2x80x94and even standard practicexe2x80x94to perform the last discharge with a part which will give an overweight to the portion because it will be an almost lucky coincidence if among the arriving and already weighed parts there will be one which will provide the precise desired total weight.
In the last mentioned method a noticeable improvement has been achieved, cf. GB-C-2,116,732, in that based on a qualified estimate of the freight distribution in the mass of parts one causes a selective sorting out in such a manner that parts with a weight above and below the average, respectively, are brought together to make part portions which in order to fill to the desired weight need only one or a few parts which have the average weight. The method hence is based on the probability consideration that, of the normal distribution, there will be the largest number of those parts which have the respective average weight, whereby the final filling of the portions may occur the fastest when the waiting is for parts of in particular this group.
This method is quite advantageous, once it has been ascertained beforehand, by sampling, what the average weight of the parts is, and in which weight range the parts occur, i.e. what the so-called spread is. The current calculations, based on a preprogrammed normal distribution curve, may be performed with limited data (equipment, a.o. because according to normal practice one may allow that a new part may simply be fed to the first of such part portions which waits for a part in the weight class represented by that part, even though, as will be discussed below, the part might have been placed more appropriately in another of these part portions.
However, it has been realized in practice that certainly within the area of the food industry dealt with here it is difficult to retain the knowledge about the weight distribution in the mass of parts as both the average weight and the spread may fluctuate between e.g. different loads of raw material. Furthermore it is in connection with the present invention considered that it may be desirable to create particular assortments from a given mass of parts which would completely change the image of the distribution of the mass which is available for the creation of the portions discussed. As an example, the removal of in particular those parts which have the average weight may entail that there will be no parts available for the conclusion of the portions according to the method described above.
It is a well known practice that a charge is sorted beforehand, e.g. by taking out particular qualities. The portioning equipment could be better utilized if this sorting occurred in conjunction with the portioning, but with the associated deliberate change in the part weight distribution the remaining parts usable for the portioning will no longer ex-hibit the normal distribution. In this way a sorter or batcher of the said known type is given a task which it is not suited to solve. If it is desired in the industry to work with parts which are reliably present in a normal distribution the raw materials are more expensive which again gives a more expensive finished product.
The present invention relates to a method for portioning which uses certain aspects of the accumulation weighing principle but which makes it possible to distribute the individual parts to the various collection bins for the building of portions essentially independently of the weight distribution of the product parts.
It is a modern trend in the food industry that raw materials are processed one way or the other to a still increasing extent. The raw materials as delivered to the processing industries could well exhibit a normal distribution, but over time it has been a steadily increasing problem that the processed materials, which are to be packed or batched, are no longer normally distributed. Thus, it has been practically impossible or rather expensive to effect batching to a specific target weight and therewith to a fixed price of the packings. Instead, it has become a common practice to batch desired numbers of articles, e.g. four cutlets, and to weigh the individual packings as a basis for an automatic printing of weight and price or associated labels. This technique is fairly simple, but for different reasons all the links in the chain from the processing factory over wholesalers and retailers to customers would in fact prefer packings of fixed weights and prices.
Also, there are special types of packings, which could be good candidates for a xe2x80x9cbatching to predetermined weightxe2x80x9d, even without this having crossed the minds of the relevant experts because an automatic batching would seem completely impossible. As an example, it is a well known practice that cheese manufacturers may produce not only whole cheeses, but also larger and smaller pieces of such cheeses, each packed and stamped with weight and price; in this area it is a fully established and preferred practice that the customers can choose between many different piece sizes, inasfar as the pieces will be consumed over a much longer period of time than will four cutlets. Here, the merchandise is one piece only, and that could seem impertinent for the invention. However, in the said chain these pieces are not delivered one by one, but collected in boxes, and typically a retailer will receive one or more boxes with cheese pieces, all ready packed and price marked. In this picture, a potential possibility is that the sender of the box, be it a wholesaler or a manufacturer, could batch the different pieces into the box up to a specific target weight, whereby there would be no need to arrange for a weighing of the filled boxes nor for any accounting for the summed-up weights of the relevant pieces. In many instances, however, this has been practically impossible so far, particularly when pieces of a specific weight have been sorted out, because the pieces to be batched will not, then, exhibits any kind of natural distribution. Any attempt of making such a batching economical based on expectations as to a normal distribution would be completely fruitless, and no other usable methods or means have been disclosed so far.
According to the present invention it has been realized that whatever the starting conditions are, the first higher number of individually weighed articles will be indicative of some factual weight distribution, which can be assumed to be maintained in the future, until factual observations may render it clear that there is some change in the general weight distribution. On this background it is proposed by the invention to arrange for a control unit keeping track of the weights of a plurality of previous articles for determining the factual weight distribution of the received articles. Based thereon, it is possible to statistically calculate the probability of newcoming articles to fit into the already partly established portions, and it has been found that in using the calculation results methodically for diverting the articles to portions selected in this manner, many batching jobs with non-natural article distribution can be effected with a surprisingly high efficiency.
Obviously, conditions may occur under which it would not be feasible to arrange for a batching as here discussed, e.g. if the actual articles are too awkwardly distributed for aiming at any reasonable target weight. In such cases of doubt it will be possible to carry out a test weighing of the article flow and run a simulated batching program, whereby it can be ascertained how successful a batching would be, if arranged for. Under circumstances it could even be found by subsequent analyses that an automatic batching would be feasible if another target weight was chosen or if adjustments were made to affect the weight distribution in some weight range.
As an opposite extreme it has been found that the use of the invention for the batching of normally distributed articles for a variety of distributions seems to give still better results than the said known method. However, it is still the possibility of handling articles with pronounced non-normal weight distribution which is the major aspect of the present invention.
With the invention it has been realized that with the use of a more advanced data processing system it is possible to currently create a specific picture of the factual weight distribution without relying on any predetermined or preexpected distribution curve based on general statistics. According to the invention the weights of the incoming and currently weighed parts ace methodically registered in a serial register basically of the FIFO type (First In, First Out), such that the different weights of a representative number of consecutive parts, for example the latest 50-500 parts, are recorded in such a manner that it is possible to form a histogram or a similar representation of the number of parts located within respective narrow weight ranges, e.g. 5 g as pertaining to an acceptable overweight of 10 g and an acceptable underweight of 5 g. The general picture of the weight distribution may well be rather confuse compared to some standard distribution curve, but at each moment of time it will be notorious that the last plurality of parts was weight distributed according to the said histogram. There is reason to believe, therefore, that even the following parts parts will be equally weight distributed, and the following computations may be based on that expectation.
However, should the factual weight distribution undergo a change for any reason, be it an initiated picking out of all parts of one or more specific weight ranges or a general shift of the material supply to another source of supply, the characteristic distribution histogram will soon adjust itself to the changed situation, such that it will steadily be reasonably representative for the incoming parts, fully independently of statistical norms of distribution. Thus, the histogram may clearly reflect e.g. the absence of all parts of a certain weight category, whether these parts are actually missing in the supply low or they are successively selected for separate collection in dedicated bins.
With the invention it is acknowledged that the basic philosophy of the said known method of taking advantage of the normal distribution curve is indeed advantageous, but it is also realized that it can be modified to achieve still better results, both generally and in particular whenever the factual distribution is remote from any natural standard. The normal distribution curve is a model of xe2x80x9cexpected probabilityxe2x80x9d, which holds only as long as the distribution really is normal, but according to the invention this is changed into a current analysis of xe2x80x9cfactual probabilityxe2x80x9d, based on the said histogrammic resolution of the observed weight distribution. Admittedly, the practical aspect of the invention is highly dependent of the use of modern computers that can be programmed to carry out such analyses at a minimum of time, but the invention is clear with respect to the underlying reaction criteria.
Based on the histogram it is easy to calculate the probability of the occurrence of parts in the individual weight groups, and it is correspondingly easy to determine which parts should be brought together in order to form a basic sub portion qualified to be completed with parts, not necessarily of any average weight, but otherwise being predominantly present in the supply flow in order to make up a portion of the desired total weight.
It is highly characteristic for the invention that the current results of the analyses can be used in two different ways, viz. for one thing in deciding for which bin or bins any new part will be suitable, and for another thing in deciding whether that particular part is suited better for one than for others of these bins, instead of the conventional designation of the parts just to the first available recipient calling for or accepting a new part of a specific weight subrange.
For this operation it is required that the computer carries out a detailed analysis of the probabilities of each new part to be successfully added to each of the different bins, in view of the probability of forthcoming parts to fill up the portions to the target weight, derivable from the supply histogram.
This will be a matter of carrying out a series of well defined calculations at the delivery of each new part from the weighing station for rapidly determining the most relevant receiver bin for that new part, purely based on these probability calculations and not on any kind of general expectations. The computer, keeping current account of the fill-up requirements of the individual bins, should also keep track of the histogram of the incoming parts, but this will be a less urgent matter because a noticeable change of the weight of, say, 10-20 new parts will not essentially change the histogram of e.g. 200 preceding parts. It is of course important to register such changes, but for the computer capacity it is very advantageous that these changes should not necessarily be registered immediately. This may admittedly give rise to some less perfect calculations, but only during short periods of time, until a new histogram has been more or less stabilized.
The invention is not limited to the use of a single feeding line, nor to the use of a dynamic weigher. To a given sorter system may be connected several feeding lines, each with a weigher that may well require a dwelling time of the respective parts, and the computer equipment may be correspondingly adapted to handle infeed details from several sources so as to coordinate these details with the requirements of the various receiver bins. The determination of the weight of the parts may be effected by any appropriate means, thus also by a vision equipment.